Core–Shell Bimetallic Nanozyme-Enabled Synergistic Photothermal-Electrochemical Amplification for Ultrasensitive Immunoassay

Colorimetric immunoassays based on the nanozymes offer amazing potentials in the fields of quick detection. However, the subjective nature of their visual interpretation, as well as the interference of ambient factors on color development findings, severely limit the objectivity and accuracy of quantitative analysis. To overcome these constraints, we developed a photothermal-electrochemical immunoassay by using Co₃O₄@MnCo₂O₄ core-shell nanozymes that leverage the multifunctional properties of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB). This design synergistically enhances both electrocatalytic and photothermal activities, enabling highly sensitive dual-mode detection of alpha-fetoprotein (AFP). The photothermal mode achieved a detection range of 0.1-100 ng mL^-1 with a limit of detection (LOD) of 60 pg mL^-1, while the electrochemical mode offered a range of 0.01-50 ng mL^-1 and a lower LOD of 6.2 pg mL^-1. The immunoassay integrates rapid screening, accurate quantification and cross-validation functions, breaking through the bottleneck of single-mode detection and providing a new highly sensitive and reliable solution for clinical tumor marker detection.